Comet Making Closest Approach ever to Earth

A recently discovered comet is closer than it's ever been to Earth, and stargazers in the Northern Hemisphere finally get to see it.

Called Pan-STARRS, the comet is passing within 100 million miles (160. million kilometers) of Earth on Tuesday, its closest approach. The ice ball will get even nearer the sun this weekend — just 28 million miles (45 million kilometers) from the sun. That's within the orbit of Mercury.

The comet has been visible for weeks from the Southern Hemisphere. Now the top half of the world gets a glimpse as well. The best viewing days should be next Tuesday and Wednesday, when Pan-STARRS appears next to a crescent moon at dusk in the western sky.